Lassa Fever Fact Sheet

Lassa fever is a type of hemorrhagic fever caused by the Lassa virus and is mainly transmitted by rodents. The virus was first detected in 1969 in the town of Lassa, in Borno State, Nigeria; hence, its name. Lassa is endemic to West Africa, specifically Nigeria, Liberia, Sierra Leone and Guinea. A significant number of individuals infected by the Lassa virus (~80%) do not appear to develop symptoms. The case fatality rate (CFR) has been reported to be upwards of 70%

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